Process for stabilizing propanesultone

ABSTRACT

PROPANESULTONE IS STABILIZED BY ADDING AT LEAST ONE COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC AMINES, ALICYCLIC AMINES, ARALKYLAMINES, NON-AROMATIC CYCLIC AMINES, N-ALKYL-SUBSTITUTED AROMATIC AMINES, AMINOALCOHOLS AMINE CHARACTER NITROGEN CONTAINING CARBOXYLIC ACIDS HAVING 2 TO 10 CARBON ATOMS AND THEIR ESTERS, AMIDES, PYRIDINES, QUINOLINES, AND REACTION PRODUCTS OF THESE COMPOUNDS WITH PROPANESULTONE.

United States Patent Office 3,829,438 Patented Aug. 13, 1974 ABSTRACT OF THE DISCLOSURE Propanesultone is stabilized by adding at least one compound selected from the group consisting of aliphatic amines, alicyclic amines, aralkylamines, non-aromatic cyclic amines, N-alkyl-substituted aromatic amines, aminoalcohols, amine character nitrogen containing carboxylic acids having 2 to carbon atoms and their esters, amides, pyridines, quinolines, and reaction products of these compounds with propanesultone.

2 Claims DETAILED DESCRIPTION OF THE INVENTION Field of the invention The present invention relates to a process for stabilizing the hue of propanesultone.

Description of the prior art Propanesultone is a colorless liquid or crystal having a melting point of 31 C. This compound is an important synthetic material used widely as an agent for improving the dye-ability of synthetic fibers, as a surfactant, as an additive for modified starch, etc. However, propanesultone becomes colored gradually to light yellow or, in extreme cases, to orange or reddish brown during storage and transportation at ambient temperature, or under heating, so that its commercial value is reduced. Although the prevention of coloring of propanesultone has been long sought, a satisfactory process for doing so has not been found yet.

SUMMARY OF THE INVENTION After intensive investigations on preventing the coloring of propanesultone, we have found that compounds selected from the group consisting of aliphatic amines, alicyclic amines, aralkylamines, non-aromatic cyclic amines, N-alkyl substituted aromatic amines, aminoalcohols, amine character nitrogen containing carboxylic acids having 2 to 10 carbon atoms and their esters, amides, pyridines, quinolines, and reaction products of these compounds with propanesultone have quite excellent properties for stabilizing propanesultone. The present invention has been accomplished on the basis of this finding.

The object of the invention is to provide a process for stabilizing propanesultone by adding one or more of said stabilizer compounds to propanesultone to inhibit coloring and deterioration of propanesultone at ambient temperature or at an elevated temperature for a long period of time.

As examples of the stabilizers used in the process of the present invention, there may be mentioned the following compounds.

a. Aliphatic amines: Primary amines (RNHZ), secondary amines (RR'NH) and tertiary amines (RRR"N), in which R, R and R" each is alkyl having 1 to 20 carbon atoms, or allyl, such as mono-, diand tri-ethylamine, n-propylamine, isopropylamine, n-butylamine, etc.

b. Alicyclic amines: Primary, secondary or tertiary amines, as set forth in (a), in which one of the R groups is a saturated ring having from 3 to 7 carbon atoms in v the ring and which may be substituted on the ring by hydrocarbons, such as cyclohexylamine, methylcyclohexylamine, etc.

c. Aralkylamines: Amines as set forth in (a), in which one of the R groups is (Ar) (Alk), wherein Ar is phenyl and Alk is an alkylene group of 1 to 6 carbon atoms, such as benzylamine phenethylamine, etc.

d. Non-aromatic cyclic amines: Cyclic compounds containing in the ring at least 1 nitrogen atom, such as pyrrolidine, morpholine, piperidine, piperazine, hexamethylenetetraamine, melamine, etc.

e. N-alkyl substituted aromatic amines: Compounds of the formula ArNR R wherein Ar is phenyl or phenyl substituted with a hydrocarbon group, at least one of R and R is alkyl having from 1 to -6 carbon atoms and the other of R and R is alkyl having 1 to 6 carbon atoms or H, such as N-methylaniline and N,N-dimethylaniline, etc.

f. Aminoalcohols: Compounds according to (a), in which at least one of R, R and R" is substituted with OH, such as mono-, diand tri-ethanolamine, propanolamine, 2-amino-2-methylpropanol-(1), etc.

g. Amine character nitrogen containing carboxylic acids having 2-10 carbon atoms and their esters: Nitrilotriacetic acid, nicotinic acid, methyl nicotinate, methyl picolinate, etc.

b. Amides: Formamide, dimethylformamide, acetamide, acrylamide, p-toluene-sulfonamide, nicotinic acid amide, a-pyrrolidone, e-caprolactam, etc.

i. Pyridines: Pyridine and pyridine substituted on the ring with alkyl groups having 1 to 6 carbon atoms, such as pyridine, picoline, (0;,3, or Z-methyl-S-ethylpyridine, etc.

i. Quinolines: Quinoline and quinoline substituted on the ring with alkyl groups having 1 to 6 carbon atoms, such as quinoline, methylquinoline, etc.

k. Reaction products of propanesultone: Reaction products of the above compounds (a) through (j) with propanesultonc.

The stabilized propanesultone composition of the present invention may be obtained easily by directly adding and dissolving or partially dissolving the stabilizer or stabilizers in liquid propanesultone.

From the viewpoints of the influence of the stabilizers on the purity of the propanesultone, the stabilizing efli'ect thereof and economy, the preferred amount of the stabilizer added to propanesultone is 0.01-1% by weight, based on the weight of the propanesultone treated. If necessary, two or more stabilizers may be used together in the process of the present invention.

The most preferred direct method of evaluating the stability of propanesultone or the stabilizing elfect of the stabilizer for propanesultone comprises allowing a sample to stand under ordinary storage conditions for a long period of time and determining the color change that occurs. However, this method is inconvenient, because it requires a long period of time for the evaluation. Therefore, the stabilizing eifects were compared according to an accelerated coloring test under the following special conditions.

Accelerated coloring test under heating: Thirty (30) grams of propanesultone sample were charged into a hard glass ampoule, which was then closed by fusion. The ampoule was allowed to stand at C. for a predetermined period of time. The hue of the sample was determined by measuring the Gardner number or APHA number thereof.

The process of the present invention will be further illustrated by the following representative Examples.

Example 1 Samples were prepared by mixing freshly prepared propanesultone (hue: Gardner No. 1, purity: about 99%) with 0.1 wt. percent of each of the stabilizers listed in Table 1 and were subjected to an accelerated coloring test under heating. For comparison, propanesultone containing no stabilizer and propanesultone containing the same amount of representative phenolic stabilizers were tested in the same manner. The results are shown in Table 1. The numerical values in the Table are Gardner numbers. The heating was effected in all cases at 120 C. for 90 minutes.

TABLE 1 Additive. Hue after test Aliphatic amines:

Monoethylamine (70%) 2 Diethylamine 3 Triethylamine 3 n-Propylamine 3 Isopropylamine 3 n-Butylamine 3 Alicyclic amines:

Cyclohexylamine 3 4-Methylcyclohexylamine 3 Aralkylamines:

Benzylamine 2 Phenethylamine 3 Non-aromatic cyclic amines:

Pyrrolidine 3 Morpholine 5 Piperidine 3 Piperazine 3 Hexamethylenetetramine 4 Melamine 3 N-alkyl substituted aromatic amines:

, N-methylaniline 4 N,N-Dimethylaniline 3 Aminoalcohols:

Monoethanolamine 3 Diethanolamine 3 Triethanolamine 3 Propanolamine 3 2-Amino-2-methylpropanol 3 Amine character nitrogen containing carboxylic acids having 2 to carbon atoms and theiresters:

Nitrilotriacetic acid 3 Nicotinic acid 3 Methyl nicotinate 3 Methyl picolinate 3 Amides:

Formamide 2 Dimethylformamide 2 Acetamide 3 Acrylamide 2 p-Toluenesulfonamide 4 Nicotinic acid amide 2 a-Pyrrolidone 3 e-Caprolactam 2 Pyridines:

Pyridine 2 a-Picoline 4 B-Picoline 3 'y-Picoline 3 2-Methyl-5-ethylpyridine 3 Quinolines:

Quinoline 2 Methylquinoline 2 Reaction products with propanesultone:

Reaction product of propanesultone and triethanolamine 4 Reaction product of propanesultone and pyridine 3 Controls: v

No additive 6 Hydroquinone 6 2,3-Dimethylphenol 7 3,5-Dimethylphenol 9 p-Methoxyphenol 6 Guaiacol 6 Styrenated phenol 7 Butylphenol 7 As is clearly shown in Table 1, coloration of propanesultone containing any of the stabilizers according to the present invention was less than the coloration of propanesultone per se. On the other hand, coloration of propanesultone containing a phenolic stabilizer was substantially the same as or more highly colored than was the case when no additive was used.

' Example 2 TABLE 2 Heating time (hours) Additive Gardner number No additive 2 3 4 6 8 10 N,N.-Dimethylpiperazine 2 2 2 4 4 5 Triethanolaminenn 2 2 3 4 5 6 Methylpicolinate 2 2 2 3 4 5 Pyridine 2 2 2 3 I 4 5 fl-Pieoline 2 2 3 3' 4 6 Example 3 Samples of freshly prepared propanesultone (hue: Gardner No. 2, purity: above 99%) were mixed with various amounts in the range of 0.05-1 wt. percent of 1) triethanolamine and (2) pyridine and were subjected to the accelerated coloring test under heating for 5 hours.

The results are shown in Table 3. The numerical values in the Table are Gardner numbers.

TABLE 3 Heating time (hours) Additive Amount Gardner number Triethanolamine 0 2 3 4 6 8 10 0. 05 2 2 2. 5 4 5 6 0. 10 2 2 2 3 4 6 0. 50 2 2 2 2 3 4 1. 00 2 2 2 2 3 3. 5

Pyridine 0 2 3 4 6 8 10 0. 05 2 2 2. 5 4 5 6 0. 10 2 2 2 3 4 5 0. 50 2 2 2 2 2. 5 3 1. 00 2 2 2 2 2. 5 2. 5

Example 4 Accelerated coloring tests were carried out previously to obtain some samples of propanesultone, the hues of which were dilferent from one another. The samples were vmixed with 0.1 wt. percent of (1) triethanolamine and (2) pyridine and were allowed to stand at room temperature for 200 days and the degrees of coloring were examined at the intervals stated in the following table. In the samemanner, propanesulfone containing noa'dditive was also tested as a control. The results are shown in Table 4. The numerical values in the Table are APHA numbers.

TABLE 4 Days Starting Gardner number in the test Additive APHA number Pyridine .1150 50 50 so 60 Triethanolamine.. 70 70 8O 80 Pyridine 70 70 80 8O 80 Tnethanolamine" Pyridine None 80 150 200 230 230 230 240 250 90 90 100 106 200 280 320 330 350 450 500 00 100 120 170 230 --1oo 100 no 130 140 150 200 0:00 F t- N 800 000 As clearly shown in Table 4, a remarkable correlation exists between the values obtained in the accelerated heating test and the degree of coloring after allowing the samples to stand for an extended period of time.

It is noted that triethanolamine and pyridine both have an excellent stabilization effect, i.e., an effect of preventing coloring of propanesultone samples of a wide range of quality. 30 a. primary amines RNH secondary amines RRNH Example 5 and tertiary amines RR'R"N, in which R, R and R" Reaction products of the stabilizers (a) through (j) b q ls alkyl hag/mg 1 Garbo? 2 with propanesultone were prepared by selecting a comi Sig ary 5 g i pound (A) from each of the respective groups (a) to (j) 35 a a E 9 F 5 F g e Y and reacting the same with propanesultone in an equig On nngh.avmg g 9 car 1 q molar ratio. The reaction products (B) thus obtained were t e rmg w can 6 Substituted on t e rmg y washed with a non-solvent to remove unreacted submeFhyl radlcals; stances. As an example, 4.9 grams (0.04 mol) of propanefimmes as Set forth In f Whlcl} one of the R g tf sultone were weighed into a 50 ml. conical flask. 3.2 grams 40 18 whel'eln Ar 15 P y and Alk 15 (0.04 mol) of pyridine were added dropwise and, after an alkylenfi group of 1 t0 6 Carbon atoms; the addition, it was stirred. The mixture was left stand d. nonaromatic cyclic amines containing in the ring at overnight. The formed crystals were washed with methleast one nitrogen atom selected from the group pyranol repeatedly to remove unreacted substances and then rolidine, morpholine, piperidine, piperazine, N,N'- they were drled under a reduced'nressure- 45 dimethyl piperazine, hexamethylenetetraamine and Samples were prepared by mixing freshly prepared promelamine; panesultone (11,116: Gardner Q- Punty: above 99%) e. compounds of the formula ArNR R wherein Ar is i E g amqunt of 3 phenyl, at least one of R and R is alkyl having from y welg t ca cu ated on t 6 am 0 e reqctlon pro nets 1 to 6 carbon atoms and the other of R and R is (B) and (2) an amount of 0.1% by weight calculated 50 alkyl havlng l to 6 carbon atoms or H, on the ham of the compounds (A) whlch were reacted f com ounds accordin to a in which at least one of with propanesultones to make reaction products (B). The R d R bstigtut d :Nith OH. samples were subjected to the accelerated coloring test e b under heating. For comparison, propanesultone contain- P aracter'mtrogen cntammg car oxy 10 8 ing 0.1% by weight of each of the compounds (A) and 55 havmg Garbo? P P aI 1d thfilr electfid propanesultone containing no stabilizer were tested in from P P acfd, mcotlnlc acld the same manner. The results are shown in Table 5. The me hyl Incotlnate and methyl Plcollnate; numerical values in the Table are Gardner numbers. The a es Selected from the group formamlde, dlmethheating was elfected in all cases at 120 C. for 90 minutes. ylformamide, acetamide, acrylamide, p-toluenesulfon- TABLE 5 Gardner number when (B) was added in an amount ot Gardner number Solvents used for 0.1 wt. per- 0.1 wt. perwhen 0.1 wt Compounds (A) reacted with propanesultone purification oi cent cent percent of reactionproducts calculated calculated A alone Groups Particular compounds used (B) Appearance of (B) as (B) as (A) was added (a).. Aliphatic amines Triethylamine n-Hexane White turbid paste 4 4 3 (b)- Alicyclic amines Cyclohexylamine Methanol-.. White powder.-... 3 4 8 (c) Ara1ky1amines Benzylamine Diethyl ether. White crystal--- 4 2 (d). Non-aromatic cyclic amines..- N,N-dimethyl piperazine.-- Methanol Yellow powder- 3 4 2 (e) N-alkyl substituted aromatic N,N-dimethyl aniline Acetone White powder 3 4 3 1188. (1).. A i n oaicohols Triethanolamine. Methanol do 3 3.5 2 (g). Amine character nitrogen con- .Methyl nicotinate do Pale yellowpowder 3 4 3 taining carboxylic acids and their esters. (h). amides"... Formamide n-Hexane.... Whiteturbid paste 3.5 3.5 2 (i) Pyridiues. Pyridine- Methanol White powder 3 3.5 2 (j) Quinolines.. Quinoline Diethylether Pinkpowder. 3 4 2 Blank Blank 5 6 5 amide, nicotinic acid, amide, a-pyrrolidone and ecaprolactam;

i. pyridine and pyridines substituted on the ring with alkyl groups having 1 to 6 carbon atoms;

j. Quinoline and quinolines substituted on the ring with alkyl groups having 1 to 6 carbon atoms;

k. reaction products of the above compounds 9. through j with propanesultone.

2. Propanesultone containing admixed therein from f. compounds according to a, in which at least one or R, R and R" is substituted with OH;

g. amine-character-nitrogen containing carboxylic acids having 2-10 carbon atoms and their esters selected from the group nitrilotriacetic acid, nicotinic acid,

methyl nicotinate and methyl picolinate; h. amides selected from the group formamide, dimethylformamide, acetamide, acrylamide, p-toluenesulfonabout 0.01 to 1% by Weight, based on the weight of pro- 10 panesultone, of at least one stabilizer compound selected from the group consisting of a. primary amines RNH secondary amines RR'NH and tertiary amines RR'R"N, in which R, R and R" each is alkyl having 1 to 20 carbon atoms, or allyl;

amide, nicotinic acid amide, a-pyrrolidone and ecaprolactam; i. pyridine and pyridines substituted on the ring with b. primary, secondary or tertiary amines, as set forth 15 alkyl groups having 1 to 6 carbon atoms;

in a, in which one of the R groups is a saturated ring j. quinoline and quinolines substituted on the ring having from 3 to 7 carbon atoms in the ring and with alkyl groups having 1 to 6 carbon atoms; which can be substituted on the ring by methyl k. reaction products of the above compounds a through radicals; 20 j with propanesultone.

c. amines as set forth in a, in which one of the R groups is (Ar) (Alk)-, wherein Ar is phenyl and Alk is References Cited an alkylene group of 1 to 6 carbon atoms; UNITED STATES PATENTS d. non-aromatic cyclic amines containing in the ring at least one nitrogen atom selected from the group pyr- 25 3,479,352 11/1969 Norell 260-2934 rolidine, morpholine, piperidine, piperazine, N,N'-dimethyl piperazine, hexamethylenetetraamine and melamine;

JOHN D. RANDOLPH, Primary Examiner C. M. q IAISLE, Assistant Examiner 

